The usual (uncompressed) size of InnoDB data pages is 16KB. Beginning with the InnoDB storage engine, you can use the attributes ROW_FORMAT=COMPRESSED and/or KEY_BLOCK_SIZE in the CREATE TABLE and ALTER TABLE commands to enable table compression. Depending on the combination of option values, InnoDB attempts to compress each page to 1KB, 2KB, 4KB, 8KB, or 16KB.

To create a compressed table, you might use a command like this:

CREATE TABLE name
 (column1 INT PRIMARY KEY) 
 ENGINE=InnoDB
 ROW_FORMAT=COMPRESSED 
 KEY_BLOCK_SIZE=4;

If you specify ROW_FORMAT=COMPRESSED but not KEY_BLOCK_SIZE, the default compressed page size of 8KB is used. If KEY_BLOCK_SIZE is specified, you can omit the attribute ROW_FORMAT=COMPRESSED.

Setting KEY_BLOCK_SIZE=16 most often does not result in much compression, since the normal InnoDB page size is 16KB. However, this setting may be useful for tables with many long BLOB, VARCHAR or TEXT columns, because such values often do compress well, and might therefore require fewer “overflow” pages as described in Section 3.4.2.2, “Compressing BLOB, VARCHAR and TEXT Columns”.

Note that compression is specified on a table-by-table basis. All indexes of a table (including the clustered index) are compressed using the same page size, as specified on the CREATE TABLE or ALTER TABLE command. Table attributes such as ROW_FORMAT and KEY_BLOCK_SIZE are not part of the CREATE INDEX syntax, and are ignored if they are specified (although you see them in the output of the SHOW CREATE TABLE command).